The digital trunking communication system is an important branch of the mobile communication system and applied for the command communications for group scheduling, such as government department, army, police affairs, railway, water conservancy, civil aviation, steel logistics and other professional mobile communication fields.
FIG. 1 is a schematic diagram showing the internal structure of a terminal in the existing digital trunking communication system. As shown in FIG. 1, the terminal mainly comprises a main control device 1, a peripheral circuit 2, a peripheral control chip 3 and a peripheral device 4.
The main control device 1 is a main control part of the terminal (usually, one terminal only has one main control device) and internally integrated with a CPU and a device for receiving and transmitting external signals, and is the heart of the terminal.
The peripheral circuit 2 is an auxiliary equipment of the terminal, which provides power or storage and interactive environments for the main control device 1 or the peripheral control chip 3; the peripheral circuit 2 has no capability of processing operations generally and is the hardware part of the terminal.
The peripheral control chip 3 (control chip for short) is an auxiliary equipment of the terminal, which has a certain capability of processing operations; the control chip is arranged to assist the main control device 1 to manage the peripheral circuit 2 and peripheral device 4, or process some complex information instead of the main control device 1.
The peripheral device 4 is a peripheral equipment of the terminal, provided with no capability of processing operations; the peripheral devices are peripheral I/O devices, such as Liquid Crystal Display (LCD), Light-Emitting Diode (LED), keyboard, loudspeaker, etc.
The terminal may be a mobile phone, a vehicle mounted radio station or other digital trunking terminals.
The main control device 1 manages the peripheral device 4 by sending an AT instruction to the control chip 3 instead of managing directly the control of display, sound devices, for example, of the peripheral device 4. All the AT instructions start with +, followed by a command name, such as a ring operation (RING), a calling number display (CLIP or INCOMING), a service interface display (ZCCNT), etc.
FIG. 2 is a schematic diagram showing the flow of a terminal answering a normal voice call in the existing digital trunking communication system, and the flow of the terminal answering a trunking call is similar to that of the terminal answering a normal voice call. As shown in FIG. 2, the answer flow of the terminal is as follows.
After receiving a paging message signalling from the system side, the terminal returns a paging response message signalling to the system side, and performs a display for preparing to notify a user in a manner of bright screen, for example. After receiving a channel assignment message signalling from the system side, the terminal waits for a ringing and calling number message signalling; after receiving the ringing and calling number message signalling from the system side, the main control device of the terminal sends a calling number display message (i.e., +CLIP: XXX or +INCOMING: XXX, wherein XXX is the calling number) to the control chip to inform the control chip to display the calling number and waits for an response from the user. The main control device of the terminal receives a user response message from the control chip and sends a user response message signalling to the system side. When the user response message is a positive response message, which means the user answers, the main control device of the terminal then sends a service interface display message (i.e., +ZCCNT:) to the control chip for a service interface display, and starts to answer the voice information from the system side; when the user response message is a negative response message, which means the user rejects answering, the system side then terminates the call, and the main control device of the terminal sends an end call message to the control chip to end this call.
In the technical solutions discussed above, the main control device of the terminal manages the peripheral device by sending the AT instructions to the control chip, in which the AT instructions are transmitted via a serial port with relatively low speed. Therefore, how to optimize the AT instructions between the main control device and the control chip to improve the work efficiency of the terminal, especially during a trunking call, is an important task for optimizing the terminal, even the whole digital trunking system.